Extraction and degradation of chlorophyll a and b from Alternanthera sessilis

The use of Alternanthera sessilis, which is commonly known as Mukunuwenna in Sri Lanka as a source of chlorophyll was examined. The extraction of chlorophyll was carried out using buffered 80 % (v/v) aqueous acetone. The optimum operating conditions such as solvent to A. sessilis ratio, extraction temperature and extraction time were found to be 5 mL/g, 50 °C and 45 minutes, respectively. The yield of chlorophyll a and chlorophyll b under these optimum operating conditions were 659 and 261 μg/g of A. sessilis, respectively. Mechanical grinding of A. sessilis gave a higher yield as compared to blanching and drying. Refrigeration at 15 °C was found to be ideal for storing of fresh A. sessilis up to 3 days without a considerable loss of chlorophyll content. Chlorophyll extraction could be modelled successfully using basic mass transfer equations up to 30 °C. It failed above this temperature due to the degradation effect. Kinetic study on the degradation of chlorophyll extracted from A. sessilis confirmed first order reaction model and the effect of temperature on the rate constant was also adequately modelled by the Arrhenius equation.